Bottom-up emissions and energy assessment for decommissioning offshore platform structures in the North Sea: Brent and Tern case studies

Decommissioning of offshore energy infrastructure in the North Sea presents a significant environmental challenge for operators, the supply chain, government agencies, and society. Considering the UK's 2050 net zero target, it is essential to understand the offshore oil and gas (O&G) decommissioning sector's contribution to overall emissions. Such insight is crucial for evaluating decommissioning projects and informing policy development aimed at reducing emissions and achieving net zero goals. This study proposes a bottom-up emissions and energy assessment (EEA) approach for decommissioning offshore O&G platform topside and jacket structures. The approach quantifies the greenhouse gas (GHG) emissions and energy demand associated with offshore and onshore activities during the decommissioning phase. It leverages detailed, site-specific operational data to improve the precision and reliability of these assessments and is underpinned by the latest available data from the North Sea O&G decommissioning industry. The approach is validated through application to decommissioning of platform topsides and jackets in the Brent and Tern fields. Numerical comparisons reveal acceptable differences between the energy demand and CO 2 emission estimates from this study and those reported in North Sea industry reports. The study also presents insights into the reliable EEA of decommissioning projects. • Emissions and energy assessment for decommissioning offshore platform structures. • Site-specific operational data enable more reliable assessments. • Case studies: Brent and Tern platform topsides and jackets. • Transparent approach for stakeholder analysis and decision-making in decommissioning.